The present invention relates to an apparatus for setting the delay of a time fuze of a projectile fixed from a tubular weapon or gun barrel wherein the muzzle velocity of the projectile is measured and the delay is corrected by the value measured for the muzzle velocity. More particularly, the present invention relates to such an apparatus wherein the gun barrel is provided with a magnetic field generator adjacent its muzzle and the projectile is provided with a magnetic field sensor for detecting the magnetic field in order to measure the muzzle velocity of the projectile.
Such devices are disclosed, for example, in DE-AS No. 2,605,374, corresponding to U.S. Pat. No. 4,022,102, issued May 10th, 1977. In this prior art device, a pulse is actuated with the aid of a triggering coil disposed in the gun barrel when the projectile passes through this coil. This pulse is fed to a process computer and, upon passage of the projectile, gives a signal to the computer to calculate the required information and forward it to a transmitter which then, via a transmitting coil on the gun barrel, transmits the information to the fuze disposed in the projectile, via a receiving coil mounted on the projectile, when the projectile passes through the transmitting coil. The primary drawback in this prior art arrangement is the relatively great circuitry expenditures for the process computer and the transmitter.
Furthermore, DE No. 3,307,785.A1 , corresponding to U.S. Pat. No. 4,664,013, issued May 12th, 1987, discloses a method and an apparatus for setting a projectile fuze in which the velocity of the projectile is measured in that the receiving sensor disposed in the projectile flies past two annular grooves formed in the inner surface of the gun barrel.
This detunes an oscillator which furnishes measurement pulses to determine the muzzle velocity. By employing the principle of a forward-backward counter in the fuze or detonator, the detonator can be provided with a clock pulse generator meeting limited stability requirements. The primary drawback of this prior art arrangement is the relatively inaccurate velocity measurement because the maximum frequency of the clock pulse generator is 50 MHz and thus the time resolution is only 20 ns. Moreover, the sensor emits high frequency waves so that the projectile can be located by enemy radar.
Finally, DE No. 3,404,011.A1, laid-open on Aug. 8th, 1985, discloses an arrangement with which the velocity of a projectile is measured in that two annular grooves are provided in the wall of the gun barrel to serve as the measuring base for a microwave transmit-receive device. The transmit-receive device is here accommodated in the tip of the projectile where the evaluation is also made. This prior art device also has the drawback, inter alia, that an active sensor is employed which can be located by radar.